How many antennas can be used at the base station in 5g?

Up to 256 antennas. 5G makes use of advanced new wireless technology, which has increased from the previous 2*2 MIMO to the current 4*4 MIMO; more antennas also mean taking up more space, and it is obviously unrealistic to accommodate more antennas in a device with limited space. , more MIMO can only be superimposed on the base station side. Theoretically, 5G NR can use up to 256 antennas at the base station, and through the two-dimensional arrangement of antennas, 3D beam forming can be achieved, thereby improving channel capacity and coverage.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

From 1G to 4G, the core of mobile communications is communication between people, and personal communication is the core business of mobile communications. But 5G communication is not just human communication, but also the introduction of the Internet of Things, industrial automation, and driverless driving. Communication begins to shift from communication between people to communication between people and things, and finally to communication between machines.

The fifth generation of mobile communication technology (5G) is the current peak of the development of mobile communication technology. It is also an important force that mankind hopes to not only change life, but also change society.

5G is based on 4G and puts forward higher requirements for mobile communications. It not only has new improvements in speed but also in power consumption, delay and other aspects. As a result, the business will be greatly improved, and the development of the Internet will also enter the era of smart Internet from the mobile Internet.

Three major scenarios of 5G

The International Organization for Standardization 3GPP has defined the three major scenarios of 5G. Among them, eMBB refers to high-traffic mobile broadband services such as 3D/Ultra HD video, mMTC refers to large-scale Internet of Things services, and URLLC refers to services such as driverless driving and industrial automation that require low-latency and high-reliability connections.

Through the three major scenario definitions of 3GPP, we can see that for 5G, the general view of the world communications industry is that it should not only have high speed, but also meet higher requirements such as low latency. Although high speed Still an integral part of it. From 1G to 4G, the core of mobile communications is communication between people, and personal communication is the core business of mobile communications. However, 5G communication is not only human communication, but also the introduction of the Internet of Things, industrial automation, driverless driving and other services. Communication begins to shift from communication between people to communication between people and things, until it reaches between machines and machines. Communication.

The three major scenarios of 5G obviously put forward higher requirements for communication. They not only need to solve the speed problem that has always been needed to solve, but also provide higher rates to users; they also put forward new requirements for power consumption, delay, etc. Higher requirements, some aspects have completely exceeded our understanding of traditional communications, and more application capabilities have been integrated into 5G. This puts forward higher requirements for communication technology. In these three scenarios, 5G has six basic characteristics.

Six basic characteristics of 5G

High speed

Compared with 4G, 5G requires The first problem solved is high speed. As the network speed increases, user experience and experience will be greatly improved. The network will be able to face VR/UHD services without restrictions, and services that require high network speed will be widely promoted and used. Therefore, the first feature of 5G defines the increase in speed.

In fact, like every generation of communication technology, it is difficult to say exactly what the speed of 5G is. On the one hand, the peak speed is different from the actual user experience speed. Different technologies will have different speeds in different periods. . The peak requirement for 5G base stations is no less than 20Gb/s. Of course, this speed is the peak speed and is not the experience of every user. With the use of new technologies, there is room for improvement in this speed.

Such a speed means that users can download a high-definition movie every second, and may also support VR videos. Such high speed provides opportunities and possibilities for future businesses that have high speed requirements.

Ubiquitous Network

With the development of business, network services need to be all-encompassing and widespread. Only in this way can we support richer services and be used in complex scenarios. The ubiquitous network has two levels of meaning. One is broad coverage and the other is deep coverage.

Extensive refers to the need for wide coverage in all places where our society lives. In the past, high mountains and valleys did not necessarily need network coverage because there were very few people living there. However, if 5G can be covered, a large number of sensors can be deployed to conduct environmental monitoring. , air quality and even landform changes, earthquake monitoring, which is very valuable. 5G can provide the network for more of these applications.

Depth refers to the fact that in our lives, although there is already network deployment, we need to achieve higher quality in-depth coverage. We already have a 4G network at home today, but the network quality in the bathroom at home may not be very good, and there is basically no signal in the underground parking garage. It is now acceptable. With the arrival of 5G, bathrooms, underground parking garages, etc. that previously had poor network quality can be widely covered with good 5G networks.

To a certain extent, ubiquitous network is more important than high speed. Just building a network with coverage in a few places and high speed cannot guarantee 5G service and experience. Ubiquitous network is a fundamental guarantee of 5G experience. . The three major scenarios of 3GPP do not mention ubiquitous networks, but ubiquitous requirements are implicit in all scenarios.

Low power consumption

To support large-scale IoT applications, 5G must have power consumption requirements. In recent years, wearable products have developed to a certain extent, but they have encountered many bottlenecks. The biggest bottleneck is poor experience. Take a smart watch as an example. It needs to be charged every day, even if it takes less than a day. All IoT products require communication and energy. Although communication can be achieved through a variety of means today, the supply of energy can only rely on batteries. If the communication process consumes a lot of energy, it will be difficult for IoT products to be widely accepted by users.

If the power consumption can be reduced and most IoT products can be charged once a week, or even once a month, the user experience can be greatly improved and the rapid popularization of IoT products can be promoted. eMTC evolved based on the LTE protocol. In order to be more suitable for communication between things and to reduce costs, the LTE protocol has been tailored and optimized. eMTC is deployed based on cellular networks, and its user equipment can directly access the existing LTE network by supporting 1.4MHz radio frequency and baseband bandwidth. eMTC supports uplink and downlink peak rates of up to 1Mbps. NB-IoT is built on a cellular network and only consumes approximately 180kHz of bandwidth. It can be directly deployed on GSM networks, UMTS networks or LTE networks to reduce deployment costs and achieve smooth upgrades.

NB-IoT can actually be deployed based on GSM and UMTS networks. It does not require re-building the network like the core technology of 5G. However, although it is deployed on GSM and UMTS networks, it is still a The rebuilt network has the ability to greatly reduce power consumption and is also designed to meet the needs of 5G for low-power IoT application scenarios. Like eMTC, it is an integral part of the 5G network system.

Low latency

A new scenario of 5G is the highly reliable connection of driverless and industrial automation. For information exchange between people, a delay of 140 milliseconds is acceptable, but if this delay is used for driverless driving and industrial automation, it is unacceptable. The minimum requirement for 5G latency is 1 millisecond, or even lower. This places stringent requirements on the network. 5G is an inevitable requirement for applications in these new fields.

Self-driving cars require interconnection between the central control center and the car, and between cars. In high-speed operations, when braking, information needs to be sent to the car instantly to make a decision. In response, the car will rush dozens of meters in about 100 milliseconds. This requires information to be sent to the car in the shortest delay for braking and car control reactions.

The same is true for drones. For example, if hundreds of drones are flying in formation, very small deviations will lead to collisions and accidents, which requires information to be transmitted to the flying drones within a very small delay. In the process of industrial automation, if the operation of a robotic arm is to be extremely refined and ensure the high quality and accuracy of the work, it also requires a minimum delay and the most timely response. These characteristics are not so demanding in traditional human-to-human communication, or even human-to-machine communication, because human responses are slow and do not require the high efficiency and refinement of machines. Whether it is drones, driverless cars or industrial automation, they all operate at high speeds and need to ensure timely information transmission and timely response at high speeds, which places extremely high requirements on latency.

To meet the requirements of low latency, various methods need to be found in 5G network construction to reduce latency. Technologies such as edge computing will also be adopted into the 5G network architecture.

Internet of Everything

In traditional communications, terminals are very limited. In the era of fixed telephones, telephones are defined by groups of people. In the era of mobile phones, the number of terminals has exploded, and mobile phones are defined by personal applications. In the 5G era, terminals are not defined by people, because each person may have several terminals, and each family may have several terminals.

In 2018, China’s mobile terminal users have reached 1.4 billion, mainly mobile phones. The communications industry’s vision for 5G is that each square kilometer can support 1 million mobile terminals. In the future, the terminals connected to the network will not only be our mobile phones today, but also more strange products. It can be said that every product in our lives is likely to be connected to the network through 5G. Our glasses, mobile phones, clothes, belts, and shoes may all be connected to the Internet and become smart products. Doors, windows, door locks, air purifiers, fresh air fans, humidifiers, air conditioners, refrigerators, and washing machines at home may all enter the smart era. With 5G access to the network, our homes will become smart homes.

A large number of devices in social life that were previously impossible to connect to the Internet will also be able to work online and become more intelligent. Public facilities such as cars, manhole covers, telephone poles, and trash cans used to be very difficult to manage and difficult to make intelligent. And 5G can make these devices become smart devices.

Refactoring Security

Security issues do not seem to be a basic issue discussed by 3GPP, but it should also become a basic feature of 5G.

The traditional Internet has to solve the problem of information speed and barrier-free transmission. Freedom, openness and sharing are the basic spirit of the Internet, but what is built on the basis of 5G is the intelligent Internet. The intelligent Internet is not only to realize information transmission, but also to establish a new mechanism and system for society and life. The basic spirit of the smart Internet is security, management, efficiency and convenience. Security is the first requirement of the smart Internet after 5G. Assuming that 5G is built but the security system cannot be rebuilt, it will have huge destructive power.

If our driverless system is easy to break, it will be like what is shown in the movie. Cars on the road will be controlled by hackers, smart health systems will be broken, a large number of users’ health information will be leaked, and smart homes will be compromised. If it is breached, the safety of your home will not be guaranteed at all. This situation should not happen, and if there is a problem, it cannot be solved by tinkering.

In the construction of 5G network, security issues should be solved at the bottom layer. Security mechanisms should be added from the beginning of network construction, information should be encrypted, and the network should not be open. For special service needs Establish special security mechanisms. The Internet is not completely neutral and fair. To give a simple example: In terms of network assurance, ordinary users may only have one system to ensure smooth network access, and users may face congestion. However, the intelligent transportation system requires multiple systems to ensure its safe operation and ensure its network quality. When network congestion occurs, the smooth flow of the intelligent transportation system's network must be ensured. And this system cannot be accessed by ordinary terminals for management and control.

Key technologies of 5G

As a new generation of mobile communication technology, 5G’s network structure, network capabilities and requirements are very different from those in the past. There are a large number of Technology is integrated into it. Its core technology is briefly described as follows:

OFDM-based optimized waveform and multiple access

5G adopts OFDM-based waveform and multiple access technology because OFDM technology is widely used in today's 4G LTE and Wi-Fi systems because it can be extended to large-bandwidth applications, has high spectral efficiency and low data complexity, and can well meet 5G requirements. The OFDM technology family enables enhancements such as enhanced frequency localization through windowing or filtering, improved multipath transmission efficiency among different users and services, and the creation of single-carrier OFDM waveforms for energy-efficient uplink transmission.

Realizing scalable OFDM spacing parameter configuration

Through the 15kHz spacing between OFDM subcarriers (fixed OFDM parameter configuration), LTE can support up to 20 MHz carrier bandwidth. In order to support richer spectrum types/bands (in order to connect as many devices as possible, 5G will utilize all available spectrum, such as millimeter microwave, unlicensed frequency bands) and deployment methods. 5G NR will introduce scalable OFDM spacing parameter configuration. This is crucial because when the FFT (Fast Fourier Transform) scales up for larger bandwidths, it must be ensured that processing complexity is not increased. In order to support different channel widths in multiple deployment modes, 5G NR must adapt to different parameter configurations under the same deployment and improve multi-channel transmission efficiency under a unified framework. In addition, 5G NR can also achieve carrier aggregation across parameters, such as aggregating carriers in millimeter waves and frequency bands below 6GHz.

OFDM windowing improves multiplex transmission efficiency

5G will be applied to large-scale Internet of Things, which means billions of devices will be connected to each other. 5G It is necessary to improve the efficiency of multiplex transmission to meet the challenges of large-scale IoT. In order for adjacent frequency bands not to interfere with each other, in-band and out-of-band signal radiation must be as small as possible. OFDM can implement waveform post-processing, such as time domain windowing or frequency domain filtering, to improve frequency localization.

Flexible framework design

While designing 5G NR, a flexible 5G network architecture is adopted to further improve the efficiency of 5G service multiplex transmission. This flexibility is reflected not only in the frequency domain, but also in the time domain. The 5G NR framework can fully meet the different services and application scenarios of 5G. This includes Scalable Transmission Time Interval (STTI), Self-contained integrated subframe (Self-contained integrated subframe).

Advanced new wireless technology

While 5G is evolving, LTE itself is also continuing to evolve (such as the recently implemented gigabit 4G). 5G is inevitable It is necessary to take advantage of the advanced technologies currently used in 4G LTE, such as carrier aggregation, MIMO, non-shared spectrum, etc. This includes many mature communication technologies:

• Massive MIMO: from 2×2 to the current 4×4 MIMO. More antennas also mean taking up more space. It is obviously unrealistic to accommodate more antennas in a device with limited space, so more MIMO can only be superimposed on the base station. From the current theory, 5G NR can use up to 256 antennas at the base station, and through the two-dimensional arrangement of antennas, 3D beam forming can be achieved, thereby improving channel capacity and coverage.

• Millimeter wave: The new 5G technology is applying frequency bands greater than 24GHz (commonly known as millimeter wave) to mobile broadband communications for the first time. The vast amount of available high-band spectrum delivers extreme data speeds and capacity that will reshape the mobile experience. However, the utilization of millimeter waves is not easy. Using millimeter wave frequency band transmission is more likely to cause path obstruction and loss (signal diffraction capability is limited). Typically, signals transmitted in the millimeter wave band cannot even penetrate walls. In addition, it faces problems such as waveform and energy consumption.

• Spectrum sharing: Using shared spectrum and unlicensed spectrum, 5G can be expanded to multiple dimensions, achieving greater capacity, using more spectrum, and supporting new deployment scenarios. This will not only benefit mobile operators with licensed spectrum, but will also create opportunities for players without licensed spectrum, such as wireline operators, enterprises and IoT verticals, allowing them to take full advantage of 5G NR technology. 5G NR natively supports all spectrum types and flexibly leverages new spectrum sharing models through forward compatibility.

• Advanced channel coding design: The current coding of LTE networks is not enough to cope with future data transmission needs, so a more efficient channel coding design is urgently needed to increase the data transmission rate. , and use larger coding information blocks to fit the mobile broadband traffic configuration. At the same time, we must continue to improve the performance limits of existing channel coding technologies (such as LTE Turbo). The transmission efficiency of LDPC far exceeds that of LTE Turbo, and the easy-to-parallel decoding design can be expanded to achieve higher transmission rates with low complexity and low latency.

Ultra-dense heterogeneous network

The 5G network is an ultra-complex network. In the 2G era, tens of thousands of base stations can serve the entire country. network coverage, but by 4G China has more than 5 million networks. 5G needs to support 1 million devices per square kilometer. The network must be very dense and require a large number of small base stations to support it. In the same network, different terminals require different rates, power consumption, use different frequencies, and have different QoS requirements. Under such circumstances, the network can easily cause mutual interference. 5G networks need to adopt a series of measures to ensure system performance: implementation of different services in the network, coordination solutions between various nodes, network selection, and energy-saving configuration methods, etc.

In ultra-dense networks, dense deployment causes a sharp increase in the number of cell boundaries, irregular cell shapes, and users may switch frequently and complexly. In order to meet mobility requirements, this requires new handover algorithms.

In short, a complex, dense, heterogeneous, large-capacity, multi-user network needs to be balanced, stable, and reduce interference, which requires continuous improvement of algorithms to solve these problems.

Self-organization of the network

Self-organizing network is an important technology of 5G, which is self-planning and self-configuration in the network deployment phase; self-optimization in the network maintenance phase and self-healing. Self-configuration means that the configuration of new network nodes can be plug-and-play and has the advantages of low cost and easy installation. The purpose of self-planning is to dynamically plan and execute the network, while meeting the needs of system capacity expansion, business monitoring, or optimization results. Self-healing means that the system can automatically detect, locate and troubleshoot problems, greatly reducing maintenance costs and avoiding impacts on network quality and user experience.

When SON technology is applied to mobile communication networks, its advantages are reflected in network efficiency and maintenance, while reducing operator expenditures and operating cost investments. Since existing SON technologies are all based on the perspective of their respective networks, operations such as self-deployment, self-configuration, self-optimization, and self-healing are independent and closed, and lack collaboration between multiple networks.

Network slicing

It is to divide the operator's physical network into multiple virtual networks. Each network adapts to different service requirements. This can be achieved through delay and bandwidth. , security, and reliability to divide different networks to adapt to different scenarios. Network slicing technology is used to split multiple logical networks on an independent physical network, thereby avoiding the need to build a dedicated physical network for each service, which can greatly save deployment costs.

On the same 5G network, telecom operators will slice the network into multiple different networks such as intelligent transportation, drones, smart medical, smart home and industrial control, and open them to different Operators, such a sliced ​​network also has different guarantees in terms of bandwidth and reliability capabilities, as well as different billing systems and management systems. In a sliced ​​network, each service provider does not use the same network and the same services like 4G. Many abilities become uncontrollable. The 5G slicing network can provide users with different networks, different management, different services, and different billing, allowing service providers to better use the 5G network.

Content Distribution Network

In the 5G network, there will be a large number of complex services, especially a large number of audio and video services, and some services will experience instantaneous explosions. Growth, which will affect user experience and feelings. This requires the network to be transformed to adapt to the explosive growth of content.

　The content distribution network adds a new layer to the traditional network, that is, an intelligent virtual network. The CDN system comprehensively considers information such as the connection status of each node, load conditions, and user distance, and distributes relevant content to the CDN proxy server close to the user so that the user can obtain the required information nearby, thereby easing network congestion and shortening response time. , improve response speed.

The source server only needs to send the content to each proxy server, allowing users to obtain content from the nearest proxy server with sufficient bandwidth, reducing network latency and improving user experience. The advantage of CDN technology is to quickly provide information services to users and help solve network congestion problems. CDN technology has become one of the key technologies necessary for 5G.

Device-to-device communication

This is a short-range direct data transmission technology based on cellular systems. Device-to-device communication (D2D) session data is transmitted directly between terminals without forwarding through the base station, and related control signaling, such as session establishment, maintenance, wireless resource allocation and accounting, authentication, identification, Mobility management, etc. are still the responsibility of the cellular network. The introduction of D2D communication into cellular networks can reduce the burden on base stations, reduce end-to-end transmission delays, improve spectrum efficiency, and reduce terminal transmission power. When the wireless communication infrastructure is damaged or is in a coverage blind area of ​​the wireless network, the terminal can use D2D to achieve end-to-end communication or even access the cellular network. In 5G networks, D2D communication can be deployed in both licensed and unlicensed frequency bands.

Edge computing

On the side close to the source of objects or data, an open platform integrating network, computing, storage, and application core capabilities is used to provide the nearest end Serve. Its applications are initiated on the edge side, generating faster network service responses and meeting the industry's basic needs in real-time business, application intelligence, security and privacy protection. 5G wants to achieve low latency. If the data has to be calculated and stored in the cloud and servers, and then instructions are sent to the terminal, low latency cannot be achieved. Edge computing is to establish computing and storage capabilities on the base station, complete calculations and issue instructions in the shortest time.

Software-defined network and network virtualization

The core features of SDN architecture are openness, flexibility and programmability. It is mainly divided into three layers: the infrastructure layer is located at the bottom of the network, including a large number of basic network devices. This layer processes and forwards data according to the rules issued by the control layer; the middle layer is the control layer, which is mainly responsible for the data forwarding plane. Orchestrate resources, control network topology, collect global status information, etc.; the top layer is the application layer, which includes a large number of application services and calls network resources through open northbound APIs. As a new type of network architecture and construction technology, NFV advocates the ideas of separation of control and data, softwareization, and virtualization, which brings hope to break through the difficulties of existing networks.

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